Vitamin D Supplements May Reduce Levels of Certain Vitamin D Forms

Consuming one variety of vitamin D supplement may lower levels of other forms that your body utilizes better, potentially impacting your immune response.

Our skin generates vitamin D when sunlight’s ultraviolet rays convert a protein known as 7-dehydrocholesterol into vitamin D3. With diminishing sunlight in autumn and winter, nations like the UK recommend taking supplements.

There are two primary types of these supplements: Vitamin D3, or cholecalciferol, derived from lanolin—a waxy substance found in sheep’s wool—and vitamin D2, or ergocalciferol, primarily sourced from mushrooms. It was previously believed that the choice between the two wasn’t critical.

However, Emily Brown from the University of Surrey, UK, along with her team, carried out a meta-analysis encompassing 11 previously conducted randomized controlled trials involving vitamin D supplements, with 655 participants overall.

They discovered that taking vitamin D2 could diminish your body’s concentration of vitamin D3. The reasons behind this phenomenon remain unclear, as does whether vitamin D3 supplements might lower vitamin D2 levels.

Moreover, several studies revealed that individuals taking vitamin D2 had reduced levels of vitamin D3 when compared to those not supplementing. “This is an unprecedented finding,” states Brown.

A 2022 study indicates that D2 and D3 have overlapping functions but distinct roles in immune support. For instance, vitamin D3 is seen to activate the Type I interferon signaling pathway, which acts as an initial defense against pathogens.

Brown suggests that vitamin D3 supplements could be more advantageous for most individuals than vitamin D2, yet personal factors like ingredient preferences should be considered, especially for those avoiding animal products.

She also emphasizes that individuals shouldn’t discontinue vitamin D2. “If you’re taking vitamin D2 supplements, your overall vitamin D levels should be adequate, but they are less effective and may result in a reduction of their extra functions concerning immune support.”

Ouliana Ziouzenkova at Ohio State University is studying this in older adults. The conversion of vitamin D3 to its active form, calcitriol, can reduce its efficacy, indicating that D2 supplementation may be especially beneficial for this demographic.

“If no adverse effects are evident, a vegan individual with vitamin D deficiency would be wise to opt for a D2 supplement,” explains Bernadette Moore from the University of Liverpool, UK.

Fortunately, plant-based vitamin D3 is becoming more widely available. For instance, a recent development involves gene-edited tomatoes capable of producing vitamin D3, although examinations are still ongoing.

Team member Susan Ranham New from the University of Surrey hopes the findings will highlight the importance of vitamin D supplements. “Many individuals in the UK, especially in northern areas, suffer from mild osteomalacia during winter, a condition linked to vitamin D deficiency, resulting in lethargy, bone pain, muscle issues, and increased sensitivity to infections and fatigue.”